You know about the geography of the world. The topics you may know about include borders, cities, climate, countries, exports and trade, lands, maps, stars, and terrain.
Synergy: 5 or more ranks in Knowledge (Geography) gives you a +2 bonus to Navigate checks. Also, 5 or more ranks in a Knowledge skill related to the topic being investigated gives you a +2 bonus to Research checks. These bonuses increase by +1 for every additional 10 ranks (that is, +3 at 15 ranks, +4 at 25 ranks, and so on).